Systems that provide for point-of-care testing of analytes are important for doctors, health professionals, and consumers. Point-of-care testing may allow for rapid results that replicate or approach the accuracy and precision available for laboratory testing. One type of point-of-care testing relies on lateral flow test strips and the use of antibodies and markers in order to determine the concentration of various analytes. As part of such a lateral flow assay, a premix step with a buffer or other reagents may be useful. Instead of providing a user in a point-of-care setting with test tubes and a vial or reagent, a “sampler” may be provided that receives a sample and includes a premixed reagent (in many cases, a buffer). The sampler then may be used to readily apply the sample to a lateral flow test strip. This greatly increases the usability of the system for consumers and other health professionals, since no test tubes are required. One downside of such samplers is that they may contain only one compartment, so if multiple reagents or substances are used, they may need to be premixed and stored in the sampler together. This may decrease the effective life of such reagents.